The inmate,
Glen Sharkany
, 40, of Westport, allegedly made the threat from the prison, where he is serving a five-year sentence for a conviction last August of sexual assault in a spousal or cohabitating relationship.

The case was handled in Waterbury Superior Court, according to
Judicial Branch
records, which also indicate he was arrested last June by Naugatuck police for the offense, alleged to have been committed April 1, 2008.

Federal prosecutors said Tuesday that Sharkany sent a letter to the
Norwalk Social Security
office on Sept. 28 from prison -- he has been behind bars since June 9 -- in which he had placed a diagram of an explosive device that included the words "I'm going to blow up your office and the IRS office as well."

Sharkany was charged with making a bomb threat and conveying false and misleading information regarding the threat. If convicted on both counts, federal prosecutors said he could face a 10-year prison term and $250,000 fine on each count.